Describe and evaluate Gregory’s top down/indirect theory of perceptual organisation (24 marks)
Gregory proposed that our past experience, knowledge, expectations and motivations can affect how we interpret the visual information we receive, therefore affecting our perception. He suggested that how we see objects is highly brain driven and indirect, and the process takes place so fast that we are unaware of the object in ‘normal perception’; Gregory would say that ‘a perceived object is a hypothesis’.
Perceptual constancies show how the brain compensates to provide a constant perception of things despite changes in the sensory information received by the retina. For example size constancy. When we see a person an extremely small person walking next to a person of normal size we understand that a person cannot physically be that small, and therefore must be further away. Another perceptual constancy is shape constancy, where we understand that a shape is the same regardless of which angle we see it from, even though it may produce different shapes on the retina. We also see different shades of a colour (changed due to illumination) as the same colour due to colour constancy. Similarly we see the world as the same even when we are in different positions or in movement, due to location constancy.
The Top Down Theory is supported by studies of perceptual set which show how perception is affected by expectation and context. Palmer’s study supports the Top Down Theory. In this Palmer showed participants a familiar scene (such as a kitchen) and then shown a picture on a screen very quickly. This would either be an appropriate object to the scene like a loaf of bread or an inappropriate object to the scene like a drum. It was found that the loaf of bread was correctly identified 84% of the time and the drum was identified only 50% of the time. This supports Gregory as it shows that perception is influenced by the brain and what it expects to see, not what is actually there. To evaluate Palmer’s study his study could be argued to lack ecological validity as it was
Perceptual constancies show how the brain compensates to provide a constant perception of things despite changes in the sensory information received by the retina. For example size constancy. When we see a person an extremely small person walking next to a person of normal size we understand that a person cannot physically be that small, and therefore must be further away. Another perceptual constancy is shape constancy, where we understand that a shape is the same regardless of which angle we see it from, even though it may produce different shapes on the retina. We also see different shades of a colour (changed due to illumination) as the same colour due to colour constancy. Similarly we see the world as the same even when we are in different positions or in movement, due to location constancy.
The Top Down Theory is supported by studies of perceptual set which show how perception is affected by expectation and context. Palmer’s study supports the Top Down Theory. In this Palmer showed participants a familiar scene (such as a kitchen) and then shown a picture on a screen very quickly. This would either be an appropriate object to the scene like a loaf of bread or an inappropriate object to the scene like a drum. It was found that the loaf of bread was correctly identified 84% of the time and the drum was identified only 50% of the time. This supports Gregory as it shows that perception is influenced by the brain and what it expects to see, not what is actually there. To evaluate Palmer’s study his study could be argued to lack ecological validity as it was